The long-term objective of the Human Population Laboratory is to articulate relationships between social, psychological and physical patterns of living and states of individual health. In pursuit of this broad objective, the staff of the HPL has conducted: (1) a 1965 Baseline Survey, in which almost 7,000 randomly selected adult residents of Alameda County, California, provided answers to a 23-page questionnaire concerning health status and health practices; (2) a continuous follow-up of the mortality of the original sample respondents; (3) a 1974 Longitudinal Follow-Up of the surviving respondents, to measure individual changes in health status and self-reported occurrence of life-crisis events in the intervening period; (4) a 1974 Survey of approximately 3,000 randomly selected current residents of the County, to provide community trend information as well as current information on the utilization of health care facilities, unmet needs and sources of satisfaction and dissatisfaction; (5) a 1975 special supplementary survey of residents in neighborhoods with high concentrations of Spanish American families.